The present invention relates to a fluidized bed heat exchanger and, more particularly, to a support structure for supporting heat exchange tubes in the heat exchanger and for supporting the various sections of the tubes relative to each other.
The use of fluidized beds has been recognized as an attractive means of generating heat in a heat exchanger such as a boiler, a combustor, a gasifier, or the like. In these arrangements, air is passed through a bed of particulate material which normally consists of a mixture of inert material and a fossil fuel such as coal to fluidize the bed and to promote the combustion of the fuel. When the heat produced by the fluidized bed is utilized to convert water to steam such as in a steam generator, for example, the fluidized bed system offers an attractive combination of high heat release, improved heat transfer to surfaces within the bed and compact size.
In these type arrangements, a plurality of heat exchange tubes are usually connected to an external inlet header and extend in a serpentine relationship within the housing of the heat exchanger. The tubes are normally supported in an elevated position slightly above the grid plate of the heat exchanger by a refractory pier support, or the like. However, the latter does not permit an adequate flow of air, which normally flows through the grid, to those portions of the tubes which rest on the supports. Therefore, the latter tube portions become excessively hot and can lead to premature failure and hot spots within the bed. Also, if the tube sections extend across the bed for a relatively large distance, they tend to sag at their end portions and therefore do not attain a perfectly horizontal position within the housing which is important for optimum efficiency of the heat exchange process.